Automatic telephone-exchange system



June v9, 1925 1,541,388

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A L. POLINKOWSKY AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed June 13. 1923 9 Sheecs--Sheec 5 June 9, A1925.

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L. POLINKOWSKY AUToMATIc TELEPHONE EXCHANGE SYSTEM Filed June 13. 192s 9 sheets-sheet s June 9, 1925. 1,541,388

PQUNKOWSKY AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed June 13, .1923. Y Sheec's-SheeltI 6 June 9, 1925. 1,541,388

L. POLINKOWSKY AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed June 13, 1923 9 Sheets-Sheet 7 June 9, 1925. l 1,541,388

, L. PoLlNKowsKY AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed June 13. 1923 9 Sheets-Sheet 8 une 9, 192s. l1,541,388

L. POLINKOWSKY AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed June 15, 1923 9 Sheets-Sheet 9 Patented June 9, i925.

UNITE STT rr orrrc.

LIPA POLINKOWSKY, OF ANIYVERP, BELGIIUM, ASSIGNOR TO lJESE-B' ELECTRIC COMPANY, INCORPORATED, GF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

Application led .Tune 13, 1923. Serial No. 645,066.

To all '2.0710111 t may concern.'

Be it known that l, Ltr. Poninicowsnr, a citizen ot Russia, residing at Antwerp. Belgium, have invented certain new and useful improvements in Automatic Telephone-Exchange Systems, ot which the tollowing is a full, clear, concise, and exact description.

rlhis invention relates to machine switching telephone exchange systems, and more particularly, to machine switching telephone systems of the full auto-matic type in which the automatic switches are controlled by means ot a central oiticc sender having registers upon which the designations oil desired lines are recorded.

Registering mechanism tor this purpose, in accordance with the usual practice, consists oft a number of registers actuated by impulses transmitted trom the calling subscribers dial, these registers either returning to normal in response to the transmission ot revertive impulses from the automatic switches, thus insuringl the extent of movement ot such switches or connecting up particular relays oft a counting chain ot relays for measuring the extent of movement ot the switches.

It is the principal object ot the present invention to provide an improved register mechanism o't this character which will be simple and very flexible in operation permittin'g` the establishment of calls ot varying characteristics.

A Yfeature of the invention is the provision ot a registering mechanism adapte-d to record the designation ot a desired line, a portion of which mechanism is divided into a primary and a seco-ndary section. rllhe primary section consists ot a single register which registers the iii-st digit dialed by the calling subscriber and through its setting selects one ot a plurality ot registers comprising the secondary section. The second digit dialed is then recorded by the particular secondary register selected.

A further feature of the invention provides for the positioning oit the selected secondary register in the tirst or second portion of its bank in accordance with whether the first digit dialed was odd or even in value.

The remaining registers of the registering mechanism are arranged to record the remaining digits of line designations and are set successively thereby; The registers ot' thc secondary group are each provided with a number of banks of terminals which may be associated with a cross-connecting rack at which connections may be made to the counting relays of the sender. Such an arrangement permits great flexibility in the manner in which the automatic switches are controlled in accordance with the particular designation set up upon the registers.

A. 'further teature o't the invention relates to the provision of means whereby it is possible to initially operate an exchange system with a much smaller number of subscrilii-crs lines than the ultimate capacity of the system, therelt-y clin'iinatiug certain group switching stages. This is accomplished by causing the registering mechanism to skip one or more switch controlling stages should the called line designation recorded on the registers thereof necessitate the employment of a less number of switching stages than the full number ot stages provided for in its ultimate capacity.

A still turt ier feature of the invention relates to means tor stopping the selecting operation o1 the automatic switching apparatus at a definite switching stage before the tinal switching stage is reached, whereby connections such as to trunk lines leading to other exchanges may be selected in any desired number ot switching stages, the selective operation of the switching apparatus being arrested at the end oit' the proper switching stage through means associated with the registering mechanism.

A further feature resides in the provision ot means for automatically extending calls to a supervisory operators position it designations of lines which do not exist are recorded upon the registers of the registering mechanism.

These and other 'features of the invention will more readily appear by reference to the following description considered in connection with the accompanying drawings.

Fig. 1 illustrates a subscribers line, a first line finder, and at the bottom of the figure, a sender allotter individual to the link circuit of Fig. 2.

Fig. 2 shows a link circuit terminating at one end in a1 secondary line finder and at its other end in a first group selector.

Fig. 3 shows an incoming distant group selector.

Fig. 4e shows a third group selector.

Fig. 5 shows a iinal selector and one of the subscribers lines terminating in the bank of the iinal selector.

Figs. 6 to 9, inclusive, taken together show the circuits of a central oiiice register sender for controlling the setting of the selector switches. @i these figures Fig. 6 shows the primary or A code register and the register steering or progression switch. Fi'g. 7 shows the four secondary or B code registers. Fig. 8 shows the numerical registers and Fig. 9 shows the controlling and impulse measuring circuits of the sender.

Fig. 10 is a diagram illust-rating the manner in which the several iigures of the drawings should be arranged to form a complete circuit disclosure illustrating the invention. The selector switches employed and iliusstrated in Figs. 1 to 5, inclusive, may be of' the general type shown and described in the patent to Polinkowsky No. 1,193,053, issued August 1, 1916. The registering mechanism shown in Figs. 6 to 9, inclusive, is adapted to be controlled by means of a calling subscribers dial such as illustrated diagrammatically at 100, Fig. 1, of the type which transmits upon each operation thereof, a number of impulses corresponding to the value of the digit dialed. Each register A, B1, B2, B3, B4, TH, H, T and U of Figs. 6, 7 and 8 consists of a plurality of wipers mounted upon a shaft which is adapted to be rotated by means of a stepping magnet operated by impulses transmitted thereto from a subscribers dial. The register A in its several resting positions is arranged to select one of the tour secondary registers B1, B2, B3 or B4. The register steering or progression switch RS is of the same general type as the registers and serves to progressively route the several series of impulses comprising a desired line designation to the several registers.

The sender mechanism shown in Fig. 9 comprises a controlling sequence switch 920 of the well known type, a group of eleven pairs of counting relays, a portion of which have been omitted, and various control relays, the functions of'wliichwill clearly appear hereinafter. The L counting relays are connected to the banks of the numerical registers shown in Fig. 8 and to one side ot' a cross connectingrack 700 shown at the extreme right of Fig. 7 from which jumper connections may be extended as desired to the banks of the secondary registers of Fig. 7, and to the-armature contacts of relays 716, 717 and 718. By the use of this rack the terminals engaged by the brushes of the secondary registers may be readily connected to different counting relays and the control of the automatic switches by the A.

registers made very flexible. Other terminals on the rack appearing at the extreme left and extreme right of Fig. 7 may be cross connected to banks of the secondary registers as desired. The invention will be described in connection with one only the many possible cross-connecting arrangement-s.

The system disclosed as embodied in the present invention will be best understoacl from a description of the operation thereof. For this purpose it will be assumed that the subscriber whose substation is designated at L desires a connection with a subscriber whose substation is designated at M, Fig. 5, and whose directo-ry number is BY 5532. The calling subscriber upon removing his receiver 'from the switchhook establishesa circuit over the line loop for the line relay 101 extending through back contacts ofjthe' cut-oft relay 107, thereby operating the line relay. lith the line relay operated a potential is created on the test terminal 121 of the calling line, multipled to the banks of all first line finders having access thereto. This potential is connected over a path extending from the terminal 121, through the resistance 102 to battery at the contact of relay 101. circuit through the resistances 102 and 103 for the common starting relay 104, which in turn, establishes a circuit extending in parallel through the subgroup relay 106 and the peg count relay 105. If the number of subgroups of first line finders exceeds three, a second relay corresponding to 106 is also provided which is operated in parallel with relay 106. Relay 105, upon energizing, closes a circuit for the peg count meter Relay 106 prepares a circuit for the sub- Relay 101 also establishes a.

group relays 109, one of which is disclosed,

which in turn, prepare circuits through the high resistance windings of test relays 114e and through the power magnets 111 of all idle line finders in the subgroups. If more than three line finders are provided in cach subgroup, two relays corresponding to relay 109 are employed.

The circuit for the power magnet 111 of the line finder 150 disclosed may be traced from the outer right armature and contact of relay 109, through the power magnet 111, the armature and back contact of test relay 112 to battery, through the armature and back cont-act of disconnect relay 113. As soon as an idle line finder of the several which have been started finds the terminals of the calling line, the test relay 114 of such line finder becomes energized. It will be assumed that the line finder disclosed is the one that first finds the line and that the circuit for the test relay extends from battery connected to the test terminal 121, over the brush 110, the left high resistance winding of relay 11s te ground at the .outer lr-ft armature and Contact ot relay 109. Relay 114, upon energizing, connects its low resistance right-hand winding in parallel with its high resistance lett hand winding tor the purpose ot making the test terminal ogt the calling line busy to other finder switches. The circuit ot the right hand winding ci@ tends through the winding, the armature and contact of the relay, the commutator wiper 119 to ground until the brushes et the finder become properly centered upon the terminal ot the calling line when direct connection to ground through the right hand winding is opened and the right hand winding is maintained energized in series with the test relay 112. Relay 112 now becomes energized, opening` the circuit of the power magnet 111 at its armature and back contact and at its trout contact establishing a circuit extending 'from battery at the armature and contact ot relay 113. through the sto-p magnet 115 to ground through the winding ot' the common second line finder start relay 116.

)Vith relay 116 energized, a circuit is established for relay 139, which at its armatures and contacts, closes circuits for starting a plurality ot second line finders in search tor the particular first line finder trunk now connected with the calling line. It will be assumed that the line finder shown in Fig. 2 is the one that ultimately makes connection. T he starting circuit for this line inder may be traced from battery, through the outer right armature and contact of relay 139, the upper lett and lower right contacts ot cam 223, winding of relay 222, lower contact ot cam 201 1 to 3), armature and back contact of relay 234 to ground at the upper right contact o't cam 202 (1 to 2). Relay 224 is also energized in parallel therewith over a circuit extending trom the upper right contact ot cam 223 (1 to 3), winding of relay 224, upper contact of cam 200 to ground at the armature and back contact ot relay 237. Relay 224 is maintained locked over its inner right armature until after sequence switch 220 leaves position 3. Vilith relays 222 and 224 energized a circuit is closed tor the power magnet 221 of the second line finder which may be traced from battery through this power magnet, the right contact ot cam 203, the right armature and front contact ot relay 222 to ground at the outer lett armature and front contact ot relay 224. llilhen the test brush 230 ot' the second line tinder encounters potential upon the terminal 204 which was applied thereto through the operation ot' relay 112 trom battery at the armature and back Contact ot relay 113, over the armature and Front contact ot' relay 112, the right armature and back contact of relay 113, through resistance 117, a circuit is com pleted for relay 234 which may be traced from brush 230, the upper left contact of cam 223, the right high resistance winding ot relay 234, the inner left armature and trout Contact of relay 224 to ground at the upper lc'tt contact o't cani 205 (13% to 1). Relay 234, upon energizing, connects its low resistance lett winding in parallel with its high resistance right winding for the purpose of altering the potential upon the test terminal 204 to prevent the other finders which are hunting' for this terminal from stopping thereon. The circuit over which the lett winding ot relay 234 is connected may be traced through the upper contacts ot cam 223, thc lett winding of relay 234, armature and front contactoft' relay 234 to ground at the upper right contact ot cam 202 (1 to 2). At its armature and back contact relay 23-1- opens the circuit previously traced through the relay 222, which upon deenergizing. opens the circuit ot the power magnet 221. To insure that the second line tinder will stop without' overrunning the terminal of the selected trunk, a circuit is established vtor the stop magnet 225 extending from battery through the winding ot this magnet, the lower contacts o't cam 206` the rigl'it armature and back contact of relay 222 to ground at the outer left armature and front contact of relay 224. A circuit is also established in parallel therewith through the winding of sequence switch magnet 220, whereupon the sequence switch advances into position 3.

`When the sequence switch passes position 2 a circuit is established for relay 207 which may be traced from battery through the winding of this relay, the right contacts ot cam 208, the outer let't armature and back contact ot relay 209 to ground at the lower contact ot cam 210. Relay 207 establishes a circuit for relay 235 which may be traced from ground through the inner lett armature and front contact of relay 207, the winding of relay 235, brush 238, brush 11S and in parallel through the winding ot cut oit rela-y 107 ot the calling line and message register 1nagnet-103. The current iiowing in this circuit while of su'liicient strength to operate the cut oit relay 107 and relay 235, does not operate the message register 10S. Relay 235, upon energizing in this circuit, establishes a locking circuit for relay 207 eX- tending through its armature and front contact, outer lett armature and back contact ot relay 209 to ground at the lower Contact ot cam 210. ln addition to operating relay 235. relay 207 cuts the tip and ring conductors ot the trunk circuit through to the battery supply coil 231 and relay 237, over the right contact ot cam 213 and the upper contact of cam 212. Relay 237 now becomes energized over the subcribers line loop and at its armature and front contact completes the battery supply bridge through the winding of coil257. As Soon as the sequence switch Pil) leaves position 2 the circuit of relay 234 is opened at the upper left contact ot cam 228 and relay 234 unlocks, again closing at its armature and back contact a circuit for relay 222 which may be traced from battery through the lower contacts of cam 223, winding of relay 222, lower contact of cam 201, armature and back contact ot' relay 234 to ground at the contact of cani 130.

In position 3, of sequence switch 220, a circuit is established for the sender selecting sequence switch 120 which may be traced 'from battery through the magnet winding of switch 120, upper right contact of cam 211 (2/2 to 3), loweiI contact of cam 201, armature and back contact of relay 234 and thence to ground as previously traced. The switch 120 continues to rotate until an idle sender is found when battery potential will be encountered upon one of the contacts of the group of cams 124. 1t will be assumed that such an idle sender has its test lead connected to the lower contacts of cam 125 and that when these contacts are closed in position 1% to 2 of switch 120, a circuit is established i'rom battery through the upper contact of cam 900, the lower contacts of cam 125, the right contacts of cam 214, the right winding of relay 234, contact of cam 123 (l5/8) to ground at the right armature and back contact of relay 209. Relay 234, upon energizing, connects its low resistance left winding in parallel with its right winding, through the upper right contact of cam 214 (3 to 4), the right contact of cam 228 (1 to 4), the left winding armature and front of relay 234 to ground at the contact of cam 130. Through the connection of the low resistance winding 234 in parallel with the right high resistance winding the. test potential is altered at the multiples of contacts of switch 120 to prevent the seizure of the sender which has been selected by other sender selector switches. l/Vith relay 234 energized the energizing circuits previously traced for relay 222 and the selector magnet 120 are opened and as soon as relay 222 becomes deenergized a circuit is established for advancing sequence switch 220 out of position 3 into position 4. This circuit may be traced from battery through the magnet winding of switch-220, the lower right contact of cam 206 (17 to 3),.the right armature and backcontact ot relay 222 to ground at the outer' left armature and front contact of relay 224.

As soon as the sequence switch 220 leaves position 3, relays 237 and 224 become deenergized. With sequence switch 220 in position 4 a circuit is established in series through the winding of relay 222 and the windings of relay 901 of the selected register sender which may be traced from battery through the lower contacts of cam 223, winding of relay 22,2., the upper left contagia of cam 211 (4 to 41/2), the lower right contact of cam 127 (2), the left winding of relay 901, the armature and back Contact of relay 902, the inner left armature and back contact of relay 903, right contacts of cam 904, the right winding of relay 901, thence t(o )ground at the right contact of cam 905 1 in this circuit due to the inclusion of both windings of relay 901, but relay 901 energizes and establishes a circuit for relay 909 which may be traced from battery through the winding or' relay 909, the upper right Contact of cam 910 (1), the armature and contact otfrelay 901 to ground at the lower right contact ot cam 911 Relay 909, upon energizing, closes a circuit for advancing sequence switch 920 out of position 1 into position 2 which may be traced `from battery, through the magnet winding of switch 920, the lower right contact of cam 912 (1 to 4), the outer right armature and front contact of relay 909, thence tof-ground at the upper right contact of cam 913 (18 to 2). As soon as the sequence switch leaves position 1, relay 909 deenergizes.

In addition, when sequence switch 220 advances into position 4, the subscribers line became connected over a dialing circuit to the selected register sender. This dialing circuit may be traced from the impulse sender 100, over the tip side of the subscribers line, tip brushes of the first and second line finders, the outer left armature and front contact of relay 207, the lower contact of cam 212 (4 to 8), the lower left contact of cam 128 (2) to ground through the right winding of impulse relay 600; and the ring conductor of the subscribers line becomes connected over the ring brushes of the first and second line finders, thel inner right armature and front contact of relay 207, the lett contact of cam 213 (4 to 8), the lower left contact of cam 129 (2) tofbattery through the lei-'t winding of impulse relay 600. Relay 600 becomes energized over this circuit and at its armature and front contact establishes a circuit for relay 906 which may be traced from battery, through the winding of relay 906, armature and front contact of relay 600, the right contact oi cam 907 (1 to 11/2), the normal contact and wiper 601 of register A., the interrupter contact of stepping magnet 602 and thence in series over the interruptor contacts of stepping mag- Relay 222 does not become energized' nets 701, 702, 703, 704, 800, soi, 802 and 80's to ground. Relay 906, upon energizing, establishes a circuit for relay 908, which in turn, prepares a locking circuit for relay 906 for holding this relay energized after sequence switch 920 leaves position 11/2, this locking circuit extending from battery, through the winding of relay 906, the armature and front contact of relay 600, the outer left armature and back 90eme: or relay 603 to ground at the inner left armature and front contact of relay 908. With the dialing circuit established back to the subscribers line and sequence switch 920 in position 2, a dialing tone is transmitted to the calling subscriber to apprise him of the fact that the circuits are in condition to receive dialing impulses. This dialing tone is applied from battery through the interrupter 914, the primary winding ot induction coil 604, the upper left contact of cam 907 (2 to 3), and thence to ground at the `interruptor contact of stepping magnet 808, over the circuit previously traced. The interrupted current flowing in the primary winding oic induction coil 604 induces current in the secondary windings of the coil connected in series with the dialing circuit.

It has been assumed that the subscriber wishes tol make a call to the BYEN exchange and iirst dials the oliice code BY. In response to the dialing of the letter B the impulse relay 600 becomes deenergized twice. Upon its first deenergization a circuit is established in series through the relays 608 and 607, which may be traced from battery through these relays, the upper contacts ot cam 915, the right armature and back contact ot relay 606, the armature and back contact ot relay 600, the outer left armature and back contact of relay 603, to ground at the inner left arma-ture and front contact ot relay 908. Relay 906, which was initially energized over a front contact of relay 600, does not release when its circuit is opened since it is made slow to release and is therefore unaffected by the dial impulses. Re-lay 607 at its outer armature and iront contact closes a circuit extending through the wiper 609 and normal contact of switch RS to battery through the winding of stepping magnet 602 ot the A code register. At the same time a holding circuit is established for relays 608 and 607 extending through the windings of these relays, the inner armature and front con* tact ot relay 607, the interrupter contact of stepping` magnet 602, and thence through the interrupter contacts of the remaining registers to ground at the interrupter contact of magnet 808 tor maintaining relays 607 and 608 energized irrespectiveof the operation of pulsing' relay 600. Until the register A has 'fully completed its first step in response to the :first deenergization of relay 600, relay 608 at its armature and Jfront contact establishes a circuit through the stepping magnet 610 ot the register steering switch RS, which may be traced from battery, through the magnet- Winding 610, the right contacts of cam 916, thence to ground at the armature contact of relay 608. Relay 608 being slow to release maintains this circuit until the iirst series of code impulses ceases. When the first stepping impulse is completed, relay 600 energizes, opening the previously traced circuit through relays 607 and 608, and relay 607 upon deenergizing opens the previously traced circuit through stepping magnet 602, which latter magnet releases, permitting the wipers ot the register A to advance into contact with the No. 1l terminals of the banks with which they are associated. In a similar manner in response to the second impulse of the first series, the A code register advances into its second position. Following the completion of the first series of impulses, slow releasing relay 608 deenergizes and opens the circuit ot' stepping magnet 610, advancing the steering switch RS to its No. 1 position.

1n response to the transmission of impulses representing the second code letter Y, impulsing relay 600 deenergizes eight times, and since at this time steering switch RS is in position 1, the circuit previously traced from the outer armature of relay 607 now extends over wiper 609, wiper 611 an-d the No. 2 contact upon which it is resting, to battery through stepping magnet 704 of code register B4'. ln response to this series of impulses, register B4 advances to its No. 8 position in the first halt of its bank. Following the termination of this series of impulses, the circuit for stepping magnet 610 of the steering relay RS is opened, as previously described, at the armature and front contact of relay 608, and the steering switch advances its wipers to position No. 2.

lVith switch RS in position 2, the circuits ot the register sender are in condition to receive the numerical designation of the desired line, which has been assumed to be 5582. rlhe stepping circuits tor stepping magnets 800, 801, 802 and 803 are established successively in positions 2, 3, 4 and 5 ot the steering switch RS, the numerical registers being set in exactly the same man ner as the code registers and the steering switch RS advancing from position to position at the termination of each series oi' impulses. Following the transmission of the units series of impulses, steering switch RS advances into position 6. At the time the steering switch RS was in position 2 during the reception of the second series ot code impulses, a circuit was established tor relay 909 extending from battery, through the winding of this relay, the lower right contact ot' cam 910 (18 to 15), No. 2 terminal upon which wiper 612 is standing, to ground at the lower lett contact of cam 913 (17 to 14). Relay 909 upon energizing, with code register B4 set in position 8, establishes a circuit for relay 917 which may be traced from battery, through the No. 2 counting relay 928, the armature and back contact of the No. 2 counting relay 924, wiper 705 and the No. 8 terminal, which has been connected by jumper wire at the rack 700, the right winding of relay 917, the inner right armature and contact of relay 909, the upper lett contact ot cam 910, the lower right contact ot this cam, and thence to ground as previously traced over the No. 2 terminal associated with wiper 312 oit switch RS. Relay 917 upon energizing locks from ground over its lett winding and inner left armature, to battery at the lower contact of cam 918. In addition, relay 909 establishes a circuit for advancing the sequence switch 920 out ot position 2 into position 4, which may be traced from battery, through the magnetwinding of switch 920, the lower right contact oit cam 912 (1 to 4), the outer right armature and front contact of relay 909, thence to ground at the upper right contact of cam 913 (18 to 2). As soon as the sequence switch moves beyond position 3 the initial circuit through relays 917 and 923 is opened and relay 923 deenergizes.

During the movement of sequence switch 920 from position 2 to position 4, a circuit is established tor relay 921 since the connection assumed is a full mechanical connection requiring the use oi the numerical registers ot the sender. The circuit for relay 921 i' may be traced 'from battery, through the contact of this cam, the outer lett armature and contact of relay 909, wiper 708 of register B4 and the No. 8 terminal upon which it is resting, wiper 804 of the thousands register Tl-I and the normal terminal upon which it is resting, to ground through the winding ot relay 921. Relay 921 energizes and locks over its inner left armature to battery at the lower contact ci cam 918. Since it is further being assumed that the capacity ot the exchange system is not over 200,000 lines, and consequently one switching stage is being suppressed, a circuit is established at this time for relay 935 -which may be traced from battery, through the upper right and lower left contacts of cam 934, wiper 7 07 of register B4 and the No. 8 ter- `minal upon' which'it is resting, thence by jumper connection to'v'racl; terminal 7 06, winding oi' relay .935, lower contact of cam 936 (2 to 2%), upper contact of said cam (2 to :8), thence to ground through the master cam 937 of sequence switch 920 closed while the sequence switch is passing between positions 2 and 3. Relay 935 upon energizing closes an obvious circuit for relay 938, which upon energizing establishes a circuit from ground, over its inner leftl armature and front contact, through the winding of relay 935, to battery as previously traced until the sequence switch leaves position 3%, and after sequence switch 920 arrives in position 31/2 to battery through the right contact of cam 918 (3l/2 to 6).

With relay 938 energized when the sequence switch 920 reaches position 4, it does not stop as it would it' an ext-ra selection stage were required, but passes through position 4 into position 5. The circuit for sequence switch 920 may be traced from battery, through the sequence switch magnet, the right contacts ot cam 919, to ground at the outer right armature and contact of relay 938. Sequence switch 920 remains in position 5 until the thousands register has beensetby the thousands digit or until the register steering switch RS advances out of position 2, when relay 909 becomes deenerglzed and closes a circuit from battery, through the sequence switch magnet, the lower left contact of cam 912 (4to 14), the outer right armature and ba'cl'ncontact of relay 909, thence to ground'at the upper right contact of cam 913 (5)'.

Setting the first group selccorf-lvith sequence switch 920 in position 6 a fundamental circuit is established through the stepping relay 901 of the oliice sender and control relay 222 ot' the rst group selector 250. This circuit may be traced from battery, .through the lower contact o1 cam 223, winding of relay 222, upper lett contact of cam 211 (4 to 41/2), the lower right Contact ot' cam 127, left winding of relay 901, armature and back contact ot relay 902, resistance 939, lower left contact of cam 904 (1 to 6%), upper left contact of cam 922 (6), to ground at the outer right armature oit relay 938. Relays 901 and 222 both energize in this circuit, relay 901 closing a new circuit for counting relay 923 traced from battery, through the winding ot relay 923, thence as previously traced through the inner right armature and front contact oit relay 917, the lower left contact of cam 925 to 6),'tl1e armature and front contact ot' relay 901, and the lower right contact of cam 911 to ground. Counting relay 923 upon energizing establishes a locking circuit through its own winding, the winding of the No. 2 counting relay 924, the armature and liront contact of relay 923, the outer lett armature and back contact of relay 926, thence to ground at the lower contact of cam 905. Relay 924,

lll

however, does not energize in this locking circuit since its winding is shunted by ground through the front contact of stepping relay 901.

At the first group selector 250, relay 222 upon energizing establishes a circuit for advancing sequence switch 220 out of position 4 into position 5. This circuit may be traced from battery, through the magnet winding 220, the lower lett contact of cam 203 (4), the right armature and front contact ot' relay 222, thence to ground at the right coninterese tact of cam 205 (4 to 17). As soon as sequence switch 220 leaves position 41/2 the initial connection of relay 222 to the funda mental circuit is opened at the upper lett contact ot' cam 211 and relay 222 is now maintained energized over the fundamental circuit through the lower right contact of cam 211 (4% to 5), lett armature and 'front contact ot relay 222, lower contacts ot cam 256, and thence over the fundamental circuit as previously traced. As soon as sequence switch 220 leaves position 4, relay 234 deenergizes.

)Vith sequence switch 220 in position 5 and relay 222 energized, a. circuit is established for the trip spindle magnet 246 er;- tending from battery, through the winding ot this magnet, the lower contacts of cam 215, the right armature and front Contact ot relay 222, and thence to ground at the right contact ot cam 205, and the trip spindle is started into rotation. During its rotation, the trip spindle shaft interrupter springs 251 connect ground over the lower right contact of cam 211, the winding ot relay 222, to battery at cam 223 :tor holding relay 222 energized and shunting down stepping relay 901 of the sender. Upon the Vfirst deenergization oit stepping relay 901 at the time the trip spindle reaches its first brush tripping position, the shunt around the counting relay 924 is opened and this relay energizes in the locking circuit of relay 923. Upon the next energization of stepping relay 901, the No. 1 counting relay 927 energizes and locks through the winding ot the No. 1 counting relay 92S. In response to the second deenergization ot relay 901, relay 928 energizes. ln response to the next energizaation of relay 901, the No. 0 counting relay 929 energizes and locks in series with relays 902 and 930 and in response to the next deenergization of relay 901 or at the time the trip spindle magnet 248 has positioned the trip spindle in a position to trip the third set ot brushes, relays 902 and 930 become energized in the locking circuit of relay 929. Relay 902 upon energizing opens the previously traced fundamental circuit, causing the deenergization of control relay 222 ot' the irst, group selector and the consequent opening of the circuit or the trip spindle magnet 248.

Upon the energization ot relay 930, a circuit is established tor advancing sequence switch 920 out ot position 6 into position 8, which may be traced from battery, through the magnet winding ot' switch 920, the lower left contact of cam 912 (4 to 14), the outer right armature and back contact or relay 909, the left armature and back contact ot relay 931, to ground at the lett armature and 'front contact ot relay 930. Sequence switch 920 is now driven from position 6 and comes to rest in position 8. In leaving position 6,

direct locking ground is removed from the energized counting relays and the counting relays are held through resistance 940 and the upper Contact ot cam 905 through position 6% when the circuit of the counting relays is opened and they release. Relay 930 also at its right armature and contact establishes a circuit extending troni ground, through the lower lett contact of cam 131, the lower lett and upper right contacts et' cam 226, to battery through the winding oit relay'262. Relay 262 is later maintained over the lett contacts of cam 919, the outer lett armature and front contact ot relay 908, to ground at the upper' lett Contact ot cam 932 when sequence switch 920 leaves position 6%: and opens the locking circuit of relay 930.

At the irst group selector, upon the opening ot the tundamental circuit, relay 222 deenergizes and opens the circuit of the trip spindle magnet 248 and closes a circuit for advancing sequence switch 220 out ot position 5 into position 6. This circuit may be traced from battery, through the magnet winding 220, the lower right con* tact of cam 206, the right armature and back contact oi relay 222, to ground at the right contact ot cam 205. As sequence switch 220 approaches position 6, relay 222 again becomes energized over a circuit eX- tending trom battery, through the lower contacts of cam 223, the winding oi relay 222, the lower contact of cam 201, the armature and back contact ot relay 234, to ground at the outer lett armature and back contact ot relay 224. With sequence switch 220 in position 6 and relay 222 energized, a circuit is established for the brush carriage magnet 241 of the first group selector for rotating the brushes in a trunk hunting movement. rllhis circuit may be traced from battery, through the magnet 241, the upper contact of cam 203 (6), the right armature and front contact of relay 222, to ground at the upper right contact ot cam 205. When passing the trip spindle, a set of brushes depending upon the position ot the trip spindle is tripped. in the case assumed the trip spindle has taken three steps and consequently the brushes opposite the third level of the group selector bank are tripped. The presence ot a tree trunk is indicated by the existence of full battery potential on the test terminal ot such trunk, and therefore as soon as the test brush 252 encounters such test potential circuit is established from battery over test terminal 216, brush 252, the right contact of cam 228, the right high resistance winding ot relay 234, to ground at the upper contact of cam 217. Relay 234 becomes energized and connects its low resistance lett win-ding in parallel with its right high resistance winding over a circuit extending from test brush 252, the let't winding, armature and trontcontact of relay 234, to ground at the outer lett armature ot relay 224. The potential on the multiples ot test terminal 216 is now altered to such an extent that ot-her group selectors upon testing the test multiples ot the selected trunk will find such trunk busy. At its armature and back contact test relay 234 opens t-he previously traced circuit ol relay 222, which in turn opens the circuit ot carriage magnet 241 to arrest the hunting movement of the brushes. Relay 222 at its right armature and back contact now establishes a circuit tor advancing sequence switch 220 out ot position 6 into position 8, which circuit may be traced from battery, through the winding of sequence switch magnet 220, the lower right contact ot cam 206, armature and back contact ot' relay 222, thence to ground at the right contact ot cam 205. A circuit is also closed in parallel therewith over the upper right contact of cam 206 to battery through the holding magnet 245, which upon energizing serves to prevent the brushes of the switch trom over-running.

To insure that the brushes shall be properly centered upon the terminals of the selected idle trunk a locking circuit is maintained for relay 222 over the upper right contact of relay 201 (6), brush 244 and commutator 269 until the brushes are correctly centered. As soon as sequence switch 220 leaves position 71/2, the circuit through the holding magnet 245 is opened and when the sequence switch enters position 7 relay 222 again energizes over a circuit extending from battery, through the. lower contacts of cam 223, winding of relay 222, the upper lett contact of cam 201 (7%E to 10), to ground at the armature and front contact ot relay 262.

Setting Lzc distant incoming selec/ca With sequence switch 220 ot the first group selector 250 in position 8 and sequence switch 920 ot the register sender in position 8, a

fundamental circuit is extended from the sender to the distant incoming group selector 350. This circuit may be traced trom battery, through the winding ot control relay 300, the lower contact ot cam 301, the ring brush of switch 250, the upper right and lower lett contacts of cam 256, the lower right contact of cam 127, the left winding of relay 901, the armature and back contact ot relay 902, the inner le'lt armature gud back Contact ot relay 903, the upper contacts of cani 904, the lower right contact ot' cam 132, the lower lett and upper right contacts of cam 255, the tip brush of switch 250, compensating resistance 315, to ground at the right contact ot cam 302. Relays 300 and 901 energize in this circuit. At the time sequence switch 920 passed out of position 6, relay 935 dei-energized since its circuit was opened at the upper right contact of cam 918, and consequently relay 938 also deenergized. then sequence switch 920 arrived in position 8, however, relay 935 again energized over a circuit extending from battery, the right Contact ot cam 918 (8 to 14), the winding ot relay 935, the normal contacts associated with the inner lett armature of relay 938, the outer right armature and back contact ot relay 903, the upper contact ot cam 925 (8), the armature and front contact ot relay 901, thence to ground at the lower contact of cam 911.

lilith sender stepping relay 901 energized and the thousands register set into position 5, since it will be recalled that the subscriber dialed the thousands digit 5, a circuit is established for the No. 4 counting relay (not shown) extendingtrom battery, through the winding of this ielay, armature and back contact of the corresponding lower counting relay, the No. 4 counting relay leach the No. 5 terminal and wiper 804 of the thousands register, rack terminal 709, the No. 8 terminal and wipe-r 708 of the code register Bft, .i the upper lett and lower right contacts 'of cam 934, the outer lett armature and front contact ot relay 917, outer lett armature and tront contact ot relay 938, the outer right armature and back contact ot relay 903, the upper contact ot' cam 925 (8), the armature and front contact ot relay 901, thence to ground at the lower contact of cam 911. The Lipper' No. 4 counting relay energizes over this circuit and at its armature and contact locks through the winding of the corresponding lower counting relay and to ground as previously traced through the lower contact of cam 905 At group selector 350 upon the energization ot relay 300, a circuit is established extending from ground, through the right armature and front contact of relay 300, the right contacts ot cam 304, the right low resistance winding ot' relay 305, the lett contact ot cam 306 (1), the lett low resistance winding of relay 307, to battery through the lower contacts ot cam 308. Relays 305 and 307 both energize in this circuit. Relay 307 establishes a locking circuit for both of these relays extending trom ground at its armature contact,` through the contacts ot' cam 303, thence as previously traced through the. windings of relays 305 and 307 to battery at the lower contacts ot' relay 308, to insure that relay 305 shall be maintained until the sequence switch reaches position 2 regardless of the continued energization of relay 300. Relay 305 upon energizing establishes a circuit which may be traced Jfrom ground, through the upper left Contact of cam 302, the armature and front contact ot relay 305, the right contact of cam 309 (1), to battery through the magnet winding of sequence switch 320 for advancing the sequence switch into position 2. When the sequence switch leaves position 1%, the initial connection ot relay 300 to the fundamental circuit is opened at the lower contact or cam 301, but relay 300 is maintained connected to the fundamental circuit overI the contact of cam 313 (l to G), the armature and front contact of relay 300 and the lower contact of cam 310 (1%c to 2), Upon leaving position 1 relays 305 and 307 become unlocked and deenergize.

Vith relay 300 energized and sequence switch 320 in position 2, a circuit is established for the trip spindle magnet 348 which may be traced from battery, through this magnet winding, the lett contact of cam 311 (2), thence to ground at the right armature and front contact of relay 300. As the trip spindle rotates, the trip spindle cam connects the upper spring of the spring set 312 to ground, thereby establishing a holding circuit through the left armature and front cont-act ot relay 300, the contact of cam 313 and the winding ot relay 300 in shunt ot' the winding of the sender stepping relay 901. Consequently, upon each grounding ot the spring set 312, as the trip spindle passes through successive brush tripping positions the sender stepping relay 901 deenergizes. ln the well known manner, upon each deenergization of stepping relay 901 a lower counting relay of the counting relay group becomes energized until the No. counting relay 930 becomes energized in series with relay 902 when the fundamental circuit is opened at the armature and back contact of relay 902 and the circuit previously traced is established from ground at the left armature and front contact ot relay 930 for advancing sequence switch 920 out ot' position S into position 10. Upon leaving position 3% the energized counting relays unlock and deenergize. Since it was assumed that the thousands register was set into its No. 5 position corresponding to the thousands digit 5, the trip spindle was advanced to position 6 for tripping the brushes opposite the sixth level ot switch 350.

Upon the opening ot the Jfundamental circuit at the contact o't relay 902, the control relay 300 of the group selector deenergizes and opens the circuit ot the trip spindle magnet 348 to arrest the movement of the trip spindle and at the back contact ot its right armature establishes a circuit over the upper contact ot cam 309 (2 to 4) and to battery tl'nough the magnet winding 320 for advancing the sequence switch into position 3. )Vith the sequence switch in position 3 a circuit is established for control relay 300 extending from battery, through the winding oit this relay, the upper right contact of cam 301 (2 to 4), the armature and back contact of relay 305, the upper and lower lett contacts ot cam 316, the armature and back contact oit relay317,lower contacts of cam 318, and to ground through the lower springs of set 312, the lower springs of this set being closed so long as the trip spindle is in an off-normal position. Relay 300 upon energizing now establishes a circuit for the brush carriage magnet 341 which extends trom battery, through the winding ot this magnet, the upper contact of cam 311 (3), to ground at the right armature and front Contact of relay 300. rlhe brush carriage is now driven in a trunk hunting movement, the brushes opposite the sixth level ot the switch being tripped in passing the tripspindle.

As soon as an idle trunk is found extending to a third group selector, which idle group selector will be assumed to be the selector 450 shown in Fig. 4, battery potential will be encountered by the test brush 352 and test relay 305 becomes energized over a circuit extending from battery, through resistance 442, the lower contact of cam 440 (1 to 7), test brush 352, the lower right contact ot cam 306 (3), to ground through the lett high resistance winding of relay 305. Relay 305 energizes and connects its low resistance right winding in parallel with its high resistance winding over a circuit extending from brush 352, through the right winding of relay 305, the upperl right and lower lett contacts of cam 304, the armature and 'front contact of relay 305, thence as previously traced to ground at springs 312. The connection of the low resistance winding of relay 305 in the circuit of test brush 352 now alters the potential on the multiples of the test terminal of the selected trunk to prevent other selector switches from seizing this trunk. At its armature and back contact relay 305 opens the circuit of relay 300, which in turn opens the circuit of carriage magnet 341 and at its right armature and back contact closes a circuit extending over the upper contact ot cam 309 for advancing sequence switch 320 out of position 3 and into position 7 A circuit is also closed from ground at the right armature and back contact of relay 300 over the left contacts of cam 309, to battery through the holding magnet 345 for insuring that the brush carriage shall not over-run. Until the brushes are properly centered on the terminals of the selected trunk, ground potential is connected from commutator 314, over brush 32'?, the upper lett contact of cam 301 (3), to battery through the winding of relay 300 to maintain the energization of relay 300 until the switch brushes are properly centered. With sequence switch 320 in position 7, the fundamental circuit is extended over the contacts of cams 319 and 321 to the third group selector 450 (Fig. 4).

Setting the third group tseZeoz01'.-VVith the fundamental Circuit so extended and Cil sequence switch 920 of the register sender in position 10, control relay 401 of the third group selector and sender stepping relay 901 become energized for controlling the setting of the group selector 450 under the control of the hundreds register of the sender, which has been set into position 5 in response to the subscribers dialing the digit 5. The circuit over which relays 401 and 901 are energized may be traced as follows: battery, winding of relay 401, lower contact of cam 405 (1 to 11/2), ring brush of switch 350, the lower left contact of cam 321 (7 to 8), the left armature and back contact of relay 300, the lower contact of cam 310 (5 to 7), ring brush of switch 250, the upper right and lower left contacts of cam 256, the lower contact of cam 127, left winding of relay 901, armature and back contact of relay 902, inner left armature and back contact of relay 903, upper right contact of cam 904, lower contact of cam 922 (10), the outer right armature and back contact of relay 908 provided that at this time the calling subscriber has completed dialing, the lower right contact of cam 132, the lower left and upper right contacts of cam 255, tip brush of switch 250, compensating resistance 315, lower contacts of cam 319, tip brush of switch 350, to ground at the right contact of cam 402.

At the register sender on the energization 0f relay 901, under the assumption that the hundreds register H has been set into position 5, a circuit is established to the upper No. 5 counting relay, which may be traced in part from battery, through the winding of this counting relay (not shown), over the No. 5 counting relay lead, the No. 4 terminal and wiper 806 of the hundreds register, the lower left contact of cam 941 (10), the outer right armature and front contact of relay 921, the upper contact of cam 911 (10 to 14), the armature and contact of relay 901, to ground through the upper left contact of cam 913 (10 to 14). In the well known manner the energized counting `relay locks through the winding of the corresponding lower counting relay (not shown At the third group selector 450 upon the energization of relay 401, a circuit is established for relay 410 extending from battery through the right winding lof this relay, the upper conta-ct of cam 409, the low resistance left winding of relay 408, the left contacts of cam 407, to ground at the right armature and front contact of relay 401. Relay 410 upon energizing establishes a locking circuit extending through its own winding and the left winding of relay 408 for maintaining relay 408 energized until the sequence switch 420 has left position 1 regardless of the continued energization of relay 401. This locking circuit may be traced from battery, through the right winding of relay 410, the upper contact of cam 409, the left winding of relay 408, the left contacts of cam 407, contacts of cam 406, the armature and front contact of relay 410, thence to ground through the upper right and lower left contacts of cam 411. Relay 408 upon energizing closes a circuit for advancing sequence switch 420 into position 2, which may be traced from battery, through the magnet winding of the sequence switch, the upper right contact of cam 412, the armature and front contact of relay 408, thence to ground at the lower contact of cam 402. When the sequence switch leaves position 1, relays 408 and 410 unlock and deenergize. As the sequence switch leaves position 1%, the initial connection of relay 401 to the fundamental circuit is openedat the lower contact of cam 405, but this relay is maintained connected to the fundamental circuit over the contact of cam 413 (1 to 6), the left armature and front cont-act of relay 401, and the lower contact of cam 400 (1% to 2). lith sequence switch 420 in position 2 and relay 401 energized, the circuit of the trip spindle magnet 448 is completed from battery, through the winding of the trip spindle magnet, the lower left contact of cam 414, thence to ground at the right armature and front contact of relay 401.

As th-e trip spindle rotates, the trip spindle cam intermittently closes the spring contacts 415, whereupon ground is connecte-d intermittently through the upper spring of this set directly to the fundamental circuit, thereby shunting down the stepping relay 901 of the register sender. Relay 401, however, is maintained energized in the local circuit extending over the lower contact of cam 400, to ground at the springs 415. In response to each application of shunting ground by the springs 415, the stepping relay 901 of the sender deenergizes and in the well ,known manner the counting relays energize in succession, beginning with the No. 5 counting relay, until the No. 0 counting jrelay 930 energizes in series with relay 902, at which time the trip spindle of the group selector 450 will have rotated into such position as to trip the set of brushes having access to the sixth level'of the switch bank. At the register sende-r upon the energization of relay 902 t-he fundamental circuit is opened, and upon thev energization of relay 930 sequence switch 920 is advanced out of position 10 into position 12, thereby unlocking all energized counting relays and preparing the circuits of the register sender for the neXt digit selection.

At the group selector 450 upon the opening of the fundamental circuit, relay 401 deenergizes, opening the circuit of the trip spindle magnet 448 to arrest the movement of the trip spindle, and at its right armature and back contact closes a circuit eX- tending over the lower lett contact of cam 412 for advancing sequence switch 420 into position 3. `With sequence switch 420 in position 3, a circuit is established tor relay 401 which may be traced through the winding ot this relay, the right contact ot cani 405 (2 to 4), the armature and back contact of relay 408, the upper contacts of cam 475, the armature and back contact of relay 410, thence to ground through the right contacts ot cam 411 and the lower springs of the set 415. Relay 401 upon energizing closes a circuit for the brush carriage magnet 441 which may be traced from battery, through the winding ot this magnet, the upper contact ot cam 414, and to ground at the. right armature and front contact of relay 401. The brush carriage is now driven in a trunk hunting movement, the sixth setot brushes being tripped as the carriage passes the trip spin-dle. As soon as the test brush 452 encounters the test terminal ot an idle trunk, which trunk will be assumed to be the trunk terminating in switch 550 (Fig. full battery potential is encountered and test relay 408 becomes energized over a circuit which may be traced from battery, over the upper contacts of cam 522, test brush 452, the lower lett cont-act ot cam 409, to ground through the right high resistance winding et relay 408. Relay 408 thereupon energizes and connects its low resistance lett winding in parallel with its high resistance winding Jfor the purpose of altering the potential on the test multiples ot" the selected trunk to prevent other group selectors from selecting this trunk. The circuit over which the left winding is connected may be traced from brush 452, left winding` ot relay 408, the upper lett and lower right contacts of cam 407, the armature and front contact of relay7 408, the upper contacts of cam 475, the armatur-e and back contact ot relay 410, the right contacts ot cam 411, and thence to Around at springs 415. At its armature and back contact relay 408 also opens the circuit of relay 401, which in turn deenergizes and opens the cir cuit ot carriage magnet 441. Relay 401, however, does not deenergize until the brushes are properly centered upon the terminals of the selected trunk since it is held by ground potential applied from commutator segment 423 over brush 422, the upper left contact ot' cam 405 (3), and thence through the winding of relay 401. As soon as the brushes are properly cent-ered and relay 401 deencrgizes, a circuit is established tor the holding magnet 445 extending from battery, through the winding of this magnet, the lower contacts ot' cam 412, and to ground at the right armature and back contact of relay 401. A circuit is also estab lished in parallel therewith through the winding ot sequence switch magnet 420 'for advancing the sequence switch out ot position 3 and into position 7. lith the sequence switch in position 7, the fundamental circuit is extended over the lower contacts of cam 403 and the upper contact ot cam 404, and over the tip and ring brushes of group selector 450 to the tinal Selector 550.

Setting the final scZccOrr-)Vth the fundamental circuit so extended and the sequence switch 920 et the register sender in position 12, circuits are established for controlling the selector in its tens selection mov-ement in accordance with the setting of the tens register et the sender, it having been assumed that the calling subscriber has dialed the tens digit 3 and that therefore the wipers ot' the tens register T are standing in position 8. The fundamental circuit over which relays 901 and 500 are now energized may be traced trom battery, hrough the winding ot relay 500, the lower lett contact ot cam 508, the lower right contact ot cam 501, thence over the ring brush of selector 450, the upper contact of cam 404 (7 to 8), the left armature and back contact ot relay 401, the lower contact o't cain 400 (5 to 7), ring brush ot selector 350, the lower lett contact et cam 821 (7 to 8), the left armature and back contact ot relay 300, the lower contact of cam 810, thence as previously traced through the inding ot sender stepping relay 901, returning over the tip conductor ot the fundamental circuit lower contacts ot cam 408, tip brush of selector 450, to ground at the right contact of cam 504 (1 to At the register sender, relay 901 upon energizing closes a circuit for the No. 8 counting relay, which may be traced in part from battery, through the winding of the No. 3 counting relay (not shown), the No. 3 counting relay lead. the No. 3 terminal on which the wiper 807 ot the tens register T is resting. the lower right contact ot cam 941, thence as previously traced through the contact ot stepping relay 901, to ground at the upper lett contact of' cam 913. This counting relay locfks in the well known manner through the corresponding No. 3 counting relay,

At the tinal selector switch upon the energization ot relay 500 in the fundamental circuit, a circuit is established for relay 505 which may be traced trom battery, through thc lett Contact ot cam 500`y winding et relay 505, the contacts ot cani 507, the right armature and front contact ot re lay 500, thence to ground through the lett contact ot cam 508. Relay 505 upon energizing locks directly to ground through its armature and front contact and establishes a circuit for relay 512, which may be traced trom battery, through the winding of relay 512, the lower contacts ot cam 511, the lower left contact of cam 510, the contacts 

